Advancing Thoracic Spine Biomechanical Research

Abstract

The long term objective of this research was to elucidate issues with current thoracic spine testing methods and develop more accurate ways to quantify the biomechanical impact of surgical procedures or medical devices. The ability to perform thoracic spine testing with a rib cage is limited by test machine variability and experimental design inconsistency, so surgeons are left with little reliable information on the biomechanical impacts of procedures and implants. This research sought to validate a novel spine test machine, provide biomechanical data to support the inclusion of an intact rib cage when testing the thoracic spine, and quantify the biomechanical impacts of sequential Ponte osteotomies. Specific Aim 1 validated the accuracy of the spine test machine for rigidity ranges that represent cadaveric specimen rigidities present in the spine. Cervical, thoracic, and lumbar spine specimens were modeled with synthetic rubber that represented the breadth of rigidities, and testing was conducted in bending and axial rotation. The maximum machine displacement error was less than 2° for lumbar and thoracic specimens, so it is suggested that researchers use an external motion-tracking system in conjunction with the test machine when high accuracy measurements are required. Specific Aim 2 quantified the biomechanical differences of testing full cadaveric thoracic spine specimens with and without an intact rib cage. While it was presumed that the rib cage provides structural stability to the thoracic spine, the extent to which the rib cage contributes to spinal motion had not been fully quantified. Testing quantified the motion and stiffness values of an intact thoracic spine specimen, and results showed that testing without a rib cage changes both motion and stiffness values. Specific Aim 3 quantified the biomechanical impact of sequential Ponte osteotomies in cadaveric thoracic spine specimens with intact rib cages. Overall and regional changes in motion due to Ponte osteotomies were analyzed, and results showed increased flexibility in the sagittal plane on both overall and regional levels. The results from this work could provide researchers and surgeons the tools they need to better understand and improve spine procedures and implants, which could ultimately improve the quality of life for patients.